Others have described methods and systems for extracting solutes from solid material. However, such processes generally are not energy efficient. For example, in previously described systems, the separation of solute from the solid is accomplished by adding water and/or a surfactant. See, e.g. U.S. Pat. Nos. 4,434,028; 5,199,997; 5,454,878; 5,154,831; and 5,286,386. The inclusion of water introduces an additional processing step, and is undesirable in certain contexts. Also, previously described systems do not allow for continuous processing, instead using batch processing or requiring batch centrifugation. See, e.g., U.S. Pat. Nos. 5,107,874; 5,080,721; 6,569,480; 5,344,493; and U.S. Patent Publication No. 2004/0014084. Batch processing has the shortcomings that it is not as efficient as continuous processing, oftentimes can not be scaled to desired production volumes, and is economically inferior when increased to desired production scales. Furthermore, many systems require processing through multiple augers or screw conveyers, which introduces additional inefficiencies. See, e.g., U.S. Pat. Nos. 1,024,230; 1,862,945; 3,226,202; 3,941,679; 4,311,561 and U.S. Patent Publication No. 2005/236015.
There remains a need for energy and economically efficient systems for extracting solutes from solid materials that does not suffer from the above shortcomings. The present invention addresses this and other needs.